Method and apparatus for mixing and discharging the contents of an electric glass furnace



J. FERGUSON I 2,018,885 METHOD AND APPARATUS FOR MIXING AND DISCHARGING THE CONTENTS OF AN' ELECTRIC GLASS FURNACE Oct. 29, 1935.

Filed June 29, z Sheets-Shed 1' INVENTOR. J'o/m Fare-warn ATTORNEYS.

Oct. 29, 1935. 2,018,885 METHOD AND APPARATUS FOR MIXING AND DISGHARGING J. FERGUSON THE CONTENTS OF AN ELECTRIC GLASS FURNACE Flled June 29, 1934 2 Sheets-Sheet 2 ATTORNEYS. 4

mm B. k v Mn Patented one 29, .1935

-METHOD AND APPARATUS FOR MIXING ,AND DISCHARGING THE CONTENTS OF AN ELECTRIC GLASS FURNACE .John Ferguson," Indianapolis, Ind. Application June 29, 1934, Serial No. 733,081

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This invention relates to a method and apparatus for mixing and discharging the contents of an electric furnace which is particularly useful in the manufacture of glass but is equally applicable to other industries.

The principal object of the invention is to produce a furnace in which the material may be discharged in gobs or in a continuous feed without mechanical discharge apparatus and in which a thorough mixing of the ingredients is proassist or impede discharge as may be desired and which acts both magneto-motively andinductively to cause a mixing movement of the material.

Other objects and features of the invention will be understood from the accompanying drawings and the following description and claims:

Fig. 1 is a central sectional view in elevation through. an electric furnace constructed in accordance with the invention. Fig. 2 is a sectional view taken onthe line 23 of 1. Fig. 3 is a wiring diagram of the electrical connections used with the furnace when it is desired to exert both downward and upward magnetic forces upon the contents of the furnace. .Fig. 4 is-a vector diagram showing the vector relationship between the currents passing between the electrodes. Fig.

5 is a similar diagram considered at the same instance of time as Fig. 4 showing theyector relationship of the magnetic flux produced between various windings and the voltages applied to'said windings; Fig. 6 is a wiring diagram of connections used with the furnace when it is desired to exert only downward forces on the material in the furnace for discharge and to exert alternate upward and downward forces for mixing between periods of discharge. sectional view on the line 1-1 of Fig. 2 showing the relation of the internal parts and the furnacecharge. I

In the drawings, by way of illustration, there isshown a glass furnace having a hearth Ill provided with a shallow dish-shaped floor II and a conical dome or roof II. The roof I! is supported upon the hearth Ill and the edges thereof are provided with a suitable seal l3, preferably air-tight. Above the dome 12 there is provided a. hopper I for the batch material to be melted Fig. 'l is a fragmentary which communicates with the apex of the dome by means of a passage l 5. Within the dome I! there is provided a conical distributing member l6 supported upon brackets H which serves to distribute the batch material to the outer zone of the fur- 5 nace as described in my copending application. Serial No. 734,247, filed July 9, 1934. Connected to the apex of the distributing member l5 there is a pipe I! used for drawing off the gases which are the products of the chemical reactions taking 1 place in the formation of glass.

The hearth I0 is provided with a central discharge opening l9. About the periphery of the dish shaped floor ll there are provided. a. plurality of electrodes 20A, 20B, 20C, 20A, 20B, and 15 C which are preferably formed of tungsten or other suitable material. Beyond the electrodes there is provided a ring 2| of laminated magnetic material having pole pieces 22 projecting in-. wardly opposite the spaces between the .elec.- 20 trodes. About the ring 2| between each of the pole pieces there are provided windings 23A, 23B, 23C, 23A, 23B, and 236' which serve; when en.- ergized, to magnetize the said ring and to cause magnetic fluxes A, B, C, oA', B'-, and 25 2C to pass between the pole pieces as indicated in the wiring diagrams in Figs. 3 and 6.

The heating current for the batch material is supplied by a transformer 24 herein shown as having its primary windings delta-connected to 0 a set of three-phase power mains 25. One offthe' secondary windings 26A is connected to the electrodes 20A and 20A, another of said secondary windings 26B is connected to the electrodes 20B and 203', while the secondary winding 260 is connected to the electrodes 20C and 20C. The secondary circuits are isolated except within the furnace so that the only currents produced in the glass are dlametric currents between the opposite electrodes. It will be noticed that the polarity of the connections between the secondary wind ings and the electrodes is such that the phase relation of the currents passing between the elec-"' trodes is as represented by the vector diagram in Fig. 4. In this diagram, the current passing from electrode 203 to 203' is indicated by the vector ICB-B') the current passing from the electrode 20A to the electrode 20A is indlcated by the vector' I(AA') while the current passing from electrode 200 to electrode 200' is indicated by the vector I(C--C'). Thus, the currents in the material have a rotating phase relation progressing in a clockwise direction about the furnace. Since the heating current is substantially a noninductive load, thwe currents are substantially in l5 phase with .the secondary voltages induced in the transformer 24. For supplying the magnetizing current to the windings 21A, etc. there is provided a second sponding position of the secondary winding 28C.

The terminal AB is connected to a stationary contactor 2! in a timing switch II the terminal BC is connectedto a similar contactor 3|, while the :terminal CA is connected-to similar contactors 32 and 38. The switch ll is also provided with stationary contactors "A which in the diagram Fig. 3 are connected to opposite terminals of the windinss 23A and 23A.

gram, contactors 34B are connected to the windings 23B and 23B and contactors C are connected to the windings 23C and 23C.

The movable portion of the switch 3|, indicated i 1 tically at 35, carries a number of'contact members it which are positioned to engage the stationary contact member. in the movement oi the switch. In one position of the switch known as the direct position, the contact members l6 beneath the letter D in the drawings engage their corresponding stationary contact members. In the reverse position of the switch, the contact members I! beneath the letter R engage the same stationary contact members. It will be seen that when the switch is in the 'direct position, the terminals of the windings 23A and 13A are connected across the taps AB and CA, the terminals of the windings 23B and 23B are connected across the tape AB and BC, while the of the windings 23C and 230' are conacross the taps no and on Referring again particularly to Fig. 3, it will be noticed that the left-hand terminal of winding 23A is connected to the same line as the left-hand terminal of winding 23A, while the right-hand terminals of said windings are similarly connected together. Thus, the magnetic flux A will be at its maximum in a clockwise direction while the flux all is at its maximum in a counterclockwise direction. This insures that the portions of the fluxes oA and oA' cutting the current path between that the voltages applied thereto considerably the electrodes "A and 20A exert upward or downward magneto-motive forces upon the current carrying material at the same time. The

connections oi the windings 23B, 23B, 23C and 280' ar.

It is highly desirable that the various magnetic fluxes be in phase with their corresponding heating currents in order to obtain themaximum magneto-motive action. Since the windings 23A, etc. constitute an inductive load. it is necessary lead the voltages applied? to the electrodes to produce the desired phase'reiation. This is accomplished by the connection herein illustrated since the voltage between terminals CA and AB, for example, considerably leads the voltage generatedinthewinding "Awhichinturnisin phase Similarly in this dinv 'It is obvious that the taps an, no, and ca may furnace in the same direction and in phase with the rotating phase relation of the heating currents. Y

-When the switch 3| is movedto thereversel positionR,astudyofthediagramwillshowthat each of the windings 13A, etc. is connected to the same terminal taps of the transformer 11 but in the reverse Thus, the direction of the various magnetic fluxes is reversed but the said i fluxes still maintain the characteristics of a rotating magnetic field with its direction of rotation unchanged. A

By means of this construction, several desirable results are obtained. Ino'ne of the posi- 2 tions of switch 30, the motive ores exerted by the magnetic fiuxes'upon the current carrying material all act in a downward direction and thus assist the force of gravity in dis-. charging material from the discharge opening! l9. In the opposite position of the switch ll all of the magneto-motiveforces act in an upward direction and thus impede the ilow of material from the discharge opening I. At the same time, the rotating magnetic field sets up: vertical induced currents in the molten material which' act in the same manner as the currentsin' the rotor of an induction-motor and cause the contents of the glass to rotate about the furnace in the direction of rotation of the 3 field. When the field is reversed for discharge, only the polarity is reversed and it still main tains the characteristics of a rotating magnetic. field and still maintains the rotary circulation of the glass. The induced currents likewise asd sist in the heating of the 'glas so that there is no heat loss resulting therefrom. Thus, the thermal efiiciency oi the magnetic circuits is a duestion that need not be conndered.

In certain cases, the force of gravity is insufd flcientto cause the relatively viscous molten glass tobedischargedfromthefurnacesothatitis unnecessary that all of the magneto-motive, forces act upwardly to prevent discharge. For such cases, the wiring arrangement of Pig. 6 isll provided. The only diilerence between this form of wiring and that of Fig. 3 resides'in the fact that thewindings 23A, 23B and 230 are mt nently connected to their co terminals AB, BC and CA by conductors II. The windings 23A, 23B and 2 30 are connected? through the reversing switch II as before. In; the, operation of this form ,of the. apparatus,

when the switch I. is in the direct position D all of the magneto-motive forces act downward-P ly to cause discharge of the glass. When-the switch is placed in thereverse position R,-only the fluxes A, B' and'oC' are reversed. This reversal causes upward movement of the gin;

adjacent the electrodes as, 'an' and ac while,

magnetic field during discharge insures a mixing movement at that time.

In Fig. '7 there is illustrated the relation of the internal parts of the furnace to the charge during operation. The incoming batch material 40 substantially covers the magnet ring 2| and extends inwardly beyond the zone of the electrodes. The molten material 4| is confined by the batch pile and is prevented thereby from coming in, contact with the magnet ring. Such molten material as may pass beyond the zone of the electrodes as at 42 quickly solidifies due to the reduced temperature beyond the electrodes. Between adjacent electrodes the zone at solid glass and unmelted batch material extends farther into the furnace than is shown in Fig. 7 due to the absence of heating currents. The pole pieces 22 are thus similarly protected against contact with molten material.

The heat generated in the windings 23A, etc. is all transmitted to the incoming batch material and, therefore, is not lost from the furnace.

- Thus, all of the electrical energy supplied to the furnace is put to a useful purpose, either to preheat the batch, to melt the same, or to produce the desired movements of material within the furnace.

While the foregoing specification describes a preferred form of the invention as applied to a glass furnace, it is apparent that the details thereof may'be varied between wide limits without departing from the scope of the invention as defined bythe following claims.

The invention claimed is:

1. In an electric furnace, the combination of a hearth adapted to support a charge of material and having a discharge opening in the bottom thereof, a pair of electrodes positioned on opposite sides of said discharge opening, means for passing an electric current between said electrodes and through said material, and electromagnetic means arranged to produce a magnetic flux transversely cutting the path of said current. 1

2. In an electric furnace, the combination of a hearth adapted to support a charge-of material and having a discharge opening. in the bottom thereof, a pair' of electrodes positioned on opposite sides of said discharge opening, means for passing an electric current between said electrodes and through said material, and electromagnetic means arranged to produce a magnetic flux transversely cutting the path of said current in a horizontal plane whereby a vertical magneto-motive force is exerted on the material carrying'said current.

'3. In an electric furnace, the combination of a hearth adapted to support a charge of material and having a discharge opening in the bottom thereof, a pair of electrodes positioned on opposite sides of said discharge opening, means for passing anelectric current between said electrodes and through said material, electromagnetic means arranged to produce a magnetic flux transversely cutting the path of said current in a horizontal plane whereby a vertical magneto-motive force is exerted on the material carrying said current, and means for reversing the directional relation between said current and said flux whereby said force may assist or impede flow of material through said discharge opening.

4. In a furnace, the combination of a hearth adapted to carry a charge of an electrically conductive material in a fluid or semi-fluid state, said hearth having a discharge opening in the floor thereof, means for passing a plurality of see 3 alternating currents through said material in diametric paths, means for producing a plurality of alternating magnetic fluxes threading said current paths in a horizontal plane and each exerting a vertical force upon the conducting material in one of said current paths, the phase relation between said currents and said fluxes being such that substantially all of said forces act in the same direction, and means for reversing said phase relation to reverse the direction of said forces for aiding or impeding flow 'of material through said opening.

I 5. In a furnace, the combination of a hearth adapted to carry a charge of an electrically conductive material in a'fluid or semi-fluid state, said hearth having a discharge opening in the floor-thereof, means for passing a plurality of alternating currents through said material in diametric paths, means for producing a plurality of alternating magnetic fluxes threading said current paths in a horizontal plane and each exerting a vertical force upon the conducting material in one of said current paths, the phase relation between said currents and said fluxes' being such that substantially all of said forces act in the same direction, and means for varying the effective action of said fluxes for controlling the flow of material through said discharge opening.

6. In a furnace, the combination of a hearth adapted to carry a charge of an electrically conductive material in a fluid or semi-fluid state, said hearth having a discharge opening in the floor thereof, means for passing an alternating electric current through said material, means for producing a pair of alternating magnetic fluxes transversely cutting the path of said current, and means for selectively reversing the phase relation of one of said fluxes, whereby the magneto-motive force exertedthereby on said material may act in the same or in the opposite direction to the force exerted by the other of said fluxes.

'7. In a furnace, the combination of a hearth adapted to carry a charge of an electrically eonductive material in a fluid or semi-fluid state, said hearth having a discharge opening in the floor thereof, means for passing a plurality of alter-. nating electric currents through said material in diametric paths, said means including a pair of oppositely positioned electrodes for each of said paths, means for producing a plurality of alternating magnetic fluxes. each of said fluxes transversely cutting one of said current paths adjacent one of said electrodes, and means for selectively reversing the phase relation of the fluxes adjacent alternate electrodes, whereby the magnetomotive forces exerted thereby upon .said material mayact in the same direction as those exerted by the remainder of said fluxes or may act in opposite directions to cause a mixing movement' of said material.

8. In a furnace, the combination of a hearth adapted to carry a charge of an electrically conductive material in a fluid or semi-fluid state, said hearth having a discharge opening in the floor thereof, means for passing an electric current through said material, means for producing a pair of magnetic fluxes transversely cutting the path of said current, and means for selectively reversing the directional relation of said fluxes, whereby the magneto-motive forces exerted thereby upon said material may act in the same or in opposite directions.

9. In a furnace, the combination of a hearth adapted to carry a charge of an electrically coni ductive material in a fluid or semi-fluid state,

netic fluxes. each of said fluxes transversely cutsaid hearth having a discharge opening in the floor thereof, means for a plurality of electric currents through said material in diametricpatbasaidmeansincludingapairofoppositely positioned electrodes for paths, means for producing a plurality of magting one oi said current paths adjacent one of said electrodes, and means for selectively reversim the directional relation of the fluxes adiacart alternate electrodes, whereby the magnetomotive forces exerted thereby upon said material 1 mactin'the same directionasthose exerted bytheofsaidfluxesormayactin oppodte the spaces elec- .irodeameansforsaidrlngtoprm opposite directions to cause said material.

10. An electric furnace including a hearth having a central discharge opening, a plurality of electrodes spaced about the periphery of said hearth. means for electric currents betwem said electrodes, a ring of magnetic material surrolmding said electrodes and having pole pieces opposite the spaces between said eleca mixing 'action of trodes, and means for. magnetizing said ring toproduce magnetic fluxes threading the paths of said currents.

discharge ofelectrodesspacedabouttheperipheryoi'said for electric currents betweenaaidelectrodes,ar-ingofmagneticmate-- rial said electrodes and having D lhreemgneticmrxesthreadingthepathsotsaid andmeansfor a pile of laidrirmtheinneredgeofsaidpilebeinginthe aimeotsaidelectroihs.

itdmcthodotmiaingmateriai inaneiec- 'triefurnaeeineludingthestepsofeleciriecurrmtathrouhthematerialinsaidfureach of said aorases ing alternating electric currents through the material in diametric paths, said currents having a rotating phase relation, producing a rotating magnetic viieid about said furnace, said field acting inductively upon the contents of the furnace l to rotate the same and having the proper phase relation with respect to said currents to exert upward magneto-motive forces upon the current carrying material for impeding discharge. and reversing the polarity of said field without re- 10 versing its direction of rotation for exerting downward magneto-motive forces on said material to assist in discharge.

15. A method of mixing and discharging material in an electric furnace having a discharge i5 'opening in the door thereof consisting of passing a plurality of electric currents through the material in said furnace, producing a plurality of magnetic fluxes exerting downward magnetomotive for'ces upon the current carrying mate- '0 rial to assist in discharge, and reversing the polarity of some 01 said fluxes to reverse the direction of some of said magneto-motive forces i'orimpeding discharge and for causing a mis ing movement of the material between discharge periods.

16. A method of controlling the discharge of material from a furnace having a discharge opening in the floor thereof consisting in passing a plurality of electric currents through said ma- 0 teriai in diametric paths; producing a plurality of magnetic fluxes exerting downward magnetomotive forces upon the current carrying material to assist in discharge, and reversing the polarity of at least a part of said fluxes for impeding die- '6 charge between discharge periods.

17 A method of controlling the discharge of material fromafurnacehavingadischarge opening in the floor thereof consisting in passing alternating electric currents through the material in diametric paths, said currentehav-- ing a rotating phase relation. producing a rotating magnetic field about said furnace, said field having the proper phase relation with respect to said currents to exert downward magnetou motive forces on the current carrying material toassistindischargeandreversingthephased said field without reversingits direction drotation to impede discharge.

18. A method of controlling the discharged!" material from a furnace having a v discharge opening in the floor thereof consisting in passing alternating electric currents through the material in diametric paths, said currents having a rotating phase relation. producing a rotating magnetic held about said furnace, said field having the proper phase relation with respect to said currents to-exert downward magnetomotive forces on the current carrying material to assist in discharge. andreversing the polarity ofatleastaportionofsaidfleldtoimpedcdik' Phal'ge between discharge periods.

' JOHN I'IBGUQN. 

